This invention relates to a method for assaying an antigen, an antibody or a nucleic acid at a high sensitivity using polyacridinium.
Luciferase catalyzes a luminescent reaction and this enzyme has been used in the immuno-diagnosis. However, the luciferase adheres to an instrument such as the tube wall, and it is difficult to perform the accurate analysis.
In contrast, when an acridinium compound, which is a chemical luminescent substance, is used in the immuno-diagnosis, the acridinium compound does not adhere to an instrument. Therefore, it can be easily applied to labeling, and has a good luminous efficiency [EP103469A (U.S. Pat. No. 4,761,382), EP263657A (U.S. Pat. Nos. 4,745,181, 4,918,192, 5,110,932), Japanese Laid-Open Patent Application H05-255263].
However, when an acridinium compound is used as a marker in the immuno-diagnosis, only one molecule of the acridinium compound can be bound to one amino group of an antibody or an antigen. Thus, the amount of the acridinium compound bound to the antibody or the antigen is not enough, it is impossible to obtain a sufficient amount of luminescence.
The present invention is based on our new finding that, when the polyacridinium compound can be bound to the antibody or the antigen, it can be used as a marker in the immunoassay, and a large number of the acridinium compound can be bound to one molecule of the antibody or the antigen, and consequently, one molecule of the antibody or the antigen binds to a marker having a very strong luminescent intensity.
The present invention provides a method for assaying an antigen, an antibody or a nucleic acid at an ultra-high sensitivity using a polyacridinium compound.